However, the OP was wondering if deleting the email is almost as bad as
verifying you are a valid address by clicking on a fiendish "click here to
unsubscribe" in a spam email. You're right - a spammer may not care, but
someone who sells a spamming service with verified addresses might.

The spammer isn't going to get the response ... the from address has
been spoofed (in 99% of the cases), so innocent person will simply get a
confirmation that your email address is valid.

Dave:
Probably true, but does it matter for the original question? That is, this kind
of situation could be one of those that is being piloted by an innovative 1% of
spammers. A "valid" return address might or might not be "valid". I.e., just
because it was created by a spammer and receives e-mail for a spammer
(...hmmm... I wonder what might be done with a database of bogus spammer
addresses?) doesn't mean much; lots can be done with an e-mail address if the
server is compromised.
Besides, the real question doesn't necessarily involve RFC-822 nor any RFC
other than those that define the basic comm protocols. A confirmation might be
due to a flaw in Outlook or any other e-mail client. The confirmation need not
be done via SMTP.
Tom Liotta

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